170 



seiuiratcd I)y tlie li<iiii(l-cui-\ o IVoui the li(iuid-region and by the 

 vapourcitrve IVoiii the vapoiir-region. As loiig as the liqiiidciirve is 

 not situated in the vicinity of point B, the corresponding vapoor- 

 cnrve will be sitnated in tlie immediate vicinity of tlie side AC. 

 Consequently the vaponr-region is exceedingly small and is reduced 

 just as the vaponrcurve, practically to a part of — or to the whole 

 side AC. Therefore we shall call this vapourcurve the straight 

 vapourline of the region L — G in the following. Consequently we 

 distinguish within the triangle pi'actically oidy two I'egions, which 

 are separated by the liquidcurve, viz. the liquidregion and the region 

 X — G; the first reaches to the point B, the latter to the side AC. 

 The conjugation-lines liquid-gas end, therefore, all practically on the 



side AC 



When the liquidcurve comes, however, in the immediate vicinity 

 of point B, so that thei'e are liquids, which contain only exceedingly 

 little A and C, then the quantity of B in the corresponding vapours 

 will no more be negligible with respect to A and C The vapour- 

 curve will then also be situated further from the side AC, so that 

 also the vapour-region becomes larger. At sufficient decrease of 

 pressure or increase of temperature the vapour-region will cover 

 even the entire component-triangle. In that ease we must, therefore, 

 certainly distinguish between the three regions, of which the movement, 

 occurrence and disappearance have been treated already previously. 



In order to deduce the equilibrium F-\- L-\- G, we may act now 

 in the same way as we did befoi'e for a ternary vapour. We dis- 

 tinguish the following cases. 



1. The solid substance is a ternary compound. 



2. The solid substance is a binary compound of two volatile 

 components. 



3. The solid substance is a binary compound of one volatile and 

 one non-volatile component. 



4. The solid substance is one of the components. 



1. We consider firstly the case sub 1. viz. that the solid substance 

 is a ternary compound ; this is for instance the case with the 

 compound Fe.Cl, . 2HC1 . 12H,0. 



Now we imagine for instance in fig. 7, 11, 12, or 13 (I) the 

 component-triangle ABC to be drawn in such a way that the point 

 F is situated within this triangle. Curve Mm can then again 

 represent the saturationcurve under its own vapourpressure of F^ 



